In the analysis of small particles as in determining their size by optical means, it is useful to prepare a slurry by suspending the particles in an organic solvent with constant stirring to provide a homogeneous suspension. The slurry is then constantly recirculated through the analyzer during analysis.
It is well known that a reservoir can advantageously be provided as a mixing chamber so that with a stirring impeller inserted into the reservoir the particles can be thoroughly mixed. The slurry with its suspended particles is pumped from the reservoir to the analyzer and then returned to the reservoir.
With recirculating apparatus such as that described above, it is difficult to provide a leak free system. Leaking is frequently encountered in the seals at the pump shaft particularly when organic solvents are involved. It is therefore an object of this invention to provide a recirculating mixing apparatus for small volumes of slurry constructed so as to avoid the need for shaft seals and with the capability of providing both stirring and pumping action with a single moving element.